Many applications utilize the detection of photons in non-visible bands, such as photons in the infrared bands, or the X-ray bands. Surveillance is an example of one such application. Image sensors that are able to detect non-visible electromagnetic radiation are relatively costly, due in part to the chemical composition of the elements required to detect energy in such bands, and the cooling requirements of such image sensors. Moreover, such image sensors are generally lower resolution than image sensors used to capture electromagnetic radiation in the converted bands. The cost and operational requirements for such image sensors inhibits their widespread use in many applications.
Image sensors used to capture electromagnetic radiation in the converted bands, on the other hand, are relatively inexpensive, do not generally have special cooling requirements, and are of increasingly high resolution.